DB: remove shared stuff, add singleton

Add Config class

source/db/db.d

@@ -24,17 +24,17 @@ class DB {
   protected DataSource m_ds;
   protected Connection m_conn;
 
-  shared this(DBSettings settings) {
+  this(DBSettings settings) {
     this.m_settings = settings;
   }
 
-  static shared(DB) getDB(DBSettings settings) {
+  static DB getDB(DBSettings settings) {
     switch (settings.connector) {
     case DBConnector.DB_PGSQL:
       import db.pgsql;
 
       debugF!"DB type is PostgreSQL";
-      return new shared PostgresDB(settings);
+      return new PostgresDB(settings);
 
     default:
       throw new Exception("DB not supported");

source/db/pgsql.d

@@ -5,8 +5,10 @@ import db.db;
 import ddbc.core;
 import ddbc.common;
 
+import slf4d;
+
 class PostgresDB : DB {
-  shared this(Args...)(auto ref Args args) {
+  this(Args...)(auto ref Args args) {
     super(args);
   }
 
@@ -22,6 +24,8 @@ class PostgresDB : DB {
       params = PGSQLDriver.setUserAndPassword(username, password);
     }
 
+    debugF!"DB URL: %s"(url);
+
     return new ConnectionPoolDataSourceImpl(driver, url, params);
   }
 }